English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

The scalar field sector in low--energy effective field theories motivated bystring theory often contains several scalar fields, some of which possessnon--standard kinetic terms. In this paper, we study theories with two scalarfields, in which one of the fields has a non--canonical kinetic term. Thekinetic coupling is allowed to depend on both fields, going beyond the work inthe literature, which usually considers the case of the coupling to depend onthe other field only. Our aim is to study adiabatic and isocurvatureperturbations in these extended theories. Our results show that the evolutionequation for the curvature perturbation does not change when allowing thecoupling to depend on both fields, while the effective mass of the entropyperturbation changes. We find expressions for the spectral index and itsrunning at horizon crossing and at the end of inflation. We apply the formalismand study three phenomenological models, with different kinetic couplings.

Adiabatic and isocurvature perturbations in extended theories with kinetic couplings